1. Field of the Invention
The present invention relates to an electronic flash apparatus and, more particularly, to an electronic flash apparatus using a gate controlled switching device.
The present invention also relates to an electronic flash apparatus having a gate controlled switching device and, more particularly, to an electronic flash light emission control circuit for preventing a gate controlled switching device from breakdown.
2. Description of the Related Art
In recent years, as an electronic flash apparatus for a camera, an electronic flash apparatus using a gate controlled switching device, e.g., an IGBT (Insulated Gate Bipolar Transistor), is used. For example, U.S. Pat. Nos. 4,839,686 and 4,951,081 disclose electronic flash apparatuses each using an IGBT having an arrangement in which the IGBT is turned on by a light emission instruction issued by a trigger signal, and is turned off by a light emission stop instruction.
However, the electronic flash apparatuses in U.S. Pat. Nos. 4,839,686 and 4,951,081 are inconvenient because the operation timings of a flash light emitting unit and the IGBT must accurately coincide with each other. In addition, the circuit arrangements of the electronic flash apparatuses become complex due to timing synchronization. Since gate control power supply circuits are required, the cost of the electronic flash apparatuses increase, and the electronic flash apparatuses have spatial limitations.
In order to solve the problem of the above complex circuit arrangement, for example, Jpn. UM Appln. KOKAI Publication No. 4-96721 discloses an electronic flash light apparatus in which a voltage is supplied from a main capacitor to a switching device control terminal in advance only when a power supply switch is in an ON state.
In the electronic flash light apparatus, however, a plurality of transistors and Zener diodes are required to ON/OFF-control the IGBT, and two lines are required to control light emission.
For this reason, strong demand has arisen for an electronic flash apparatus capable of suppressing an increase in cost and controlling a gate controlled switching device to control light emission without complicating a circuit arrangement.
In this case, the following must be additionally considered. That is, there is also realized an electronic flash apparatus in which a gate controlled switching device is controlled by a simple circuit arrangement which prevents delay of the start of light emission and breakdown of the gate controlled switching device, suppresses a manufacturing cost, and does not have spatial limitations, thereby controlling the light emission.